Four - Peptide Bond

Four - Peptide Bond - • Formed by a condensation reaction...

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1/30/12 MCB 2000 Lecture 5 The Peptide Bond: Formation and Properties
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1/30/12 MCB 2000 Lecture 5 Formation of a Peptide Bond Condensation Reaction Water is eliminated. This reaction is carried out by a catalytic RNA located in the ribosome. (dehydration)
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1/30/12 MCB 2000 Lecture 5 A peptide chain (or protein) has directionality: What type functional group is represented in the peptide bond?
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1/30/12 MCB 2000 Lecture 5 Characteristics of the Peptide Bond: Planar
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1/30/12 MCB 2000 Lecture 5 Peptide Bond: Important Characteristics • Hybrid of 2 resonance states – C-N bond has partial double bond character – free rotation does not occur – rigid Fluctuates between a double bond and a single bond because of the double bond characteristics
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1/30/12 MCB 2000 Lecture 5 Peptide bonds exist is trans configuration Avoids steric hindrance between R-groups
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1/30/12 MCB 2000 Lecture 5 Summary: Important features of the peptide bond
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Unformatted text preview: • Formed by a condensation reaction involving the elimination of water. • Equilibrium favors reactants vs. products--energy consuming process • Covalent; kinetically stable • Planar in geometry and rigid. • Partial double bond character—resonance • Trans configuration 1/30/12 MCB 2000 Lecture 5 Phi ( ) and Psi ( ) Bond Angles • Phi ( ) refers to angle of rotation about bond between nitrogen and -carbon. • Psi ( ) refers to angle of rotation about bond between carbonyl and -carbon . 1/30/12 MCB 2000 Lecture 5 Significance of and angles • Rotation about these bonds permits proteins to fold in different ways--however, not all combinations are permissible due to steric hindrance • Suggests 2 important points with regard to protein structure: – Steric exclusion as an organizing principle – Restricted set of and angles limits number of possible structures Ramachandran Plot...
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Four - Peptide Bond - • Formed by a condensation reaction...

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